53 results found
Westhead O, Barrio J, Bagger A, et al., 2023, Near ambient N2 fixation on solid electrodes versus enzymes and homogeneous catalysts, Nature Reviews Chemistry, Vol: 7, Pages: 184-201, ISSN: 2397-3358
The Mo/Fe nitrogenase enzyme is unique in its ability to efficiently reduce dinitrogen to ammonia at atmospheric pressures and room temperature. Should an artificial electrolytic device achieve the same feat, it would revolutionise fertilizers and even provide an energy dense, truly carbon-free fuel. This Review provides a coherent comparison of recent progress made in dinitrogen fixation on (i) solid electrodes, (ii) homogeneous catalysts and (iii) nitrogenases. Specific emphasis is placed on systems for which there is unequivocal evidence that dinitrogen reduction has taken place. By establishing the cross-cutting themes and synergies between these systems, we identify viable avenues for future research.
Westhead O, Barrio J, Bagger A, et al., 2023, Author Correction: Near ambient N<inf>2</inf> fixation on solid electrodes versus enzymes and homogeneous catalysts (Nature Reviews Chemistry, (2023), 10.1038/s41570-023-00462-5), Nature Reviews Chemistry
Langley J, Purchase R, Viola S, et al., 2022, Simulating the low-temperature, metastable electrochromism of Photosystem I: Applications to Thermosynechococcus vulcanus and Chroococcidiopsis thermalis, JOURNAL OF CHEMICAL PHYSICS, Vol: 157, ISSN: 0021-9606
Viola S, Roseby W, Santabarbara S, et al., 2022, Impact of energy limitations on function and resilience in long-wavelength photosystem II, eLife, Vol: 11, ISSN: 2050-084X
Photosystem II (PSII) uses the energy from red light to split water and reduce quinone, an energy-demanding process based on chlorophyll a (Chl-a) photochemistry. Two types of cyanobacterial PSII can use chlorophyll d (Chl-d) and chlorophyll f (Chl-f) to perform the same reactions using lower energy, far-red light. PSII from Acaryochloris marina has Chl-d replacing all but one of its 35 Chl-a, while PSII from Chroococcidiopsis thermalis, a facultative far-red species, has just 4 Chl-f and 1 Chl-d and 30 Chl-a. From bioenergetic considerations, the far-red PSII were predicted to lose photochemical efficiency and/or resilience to photodamage. Here, we compare enzyme turnover efficiency, forward electron transfer, back-reactions and photodamage in Chl-f-PSII, Chl-d-PSII and Chl-a-PSII. We show that: i) all types of PSII have a comparable efficiency in enzyme turnover; ii) the modified energy gaps on the acceptor side of Chl-d-PSII favour recombination via PD1+Phe- repopulation, leading to increased singlet oxygen production and greater sensitivity to high-light damage compared to Chl-a-PSII and Chl-f-PSII; iii) the acceptor-side energy gaps in Chl-f-PSII are tuned to avoid harmful back reactions, favouring resilience to photodamage over efficiency of light usage. The results are explained by the differences in the redox tuning of the electron transfer cofactors Phe and QA and in the number and layout of the chlorophylls that share the excitation energy with the primary electron donor. PSII has adapted to lower energy in two distinct ways, each appropriate for its specific environment but with different functional penalties.
Rutherford WA, Viola S, Davis G, et al., 2022, Photosystem II bioenergetics: redox tuning, the red limit and beyond, 21st European Bioenergetics Conference (EBEC), Publisher: ELSEVIER, Pages: 3-4, ISSN: 0005-2728
Viola S, Roseby W, Santabarabara S, et al., 2022, Abstract The energetics of the two types of far-red Photosystem II, 21st European Bioenergetics Conference (EBEC), Publisher: ELSEVIER, Pages: 81-81, ISSN: 0005-2728
Viola S, Roseby W, Santabarabara S, et al., 2022, Impact of energy limitations on function and resilience in long-wavelength Photosystem II
<jats:title>Abstract</jats:title><jats:p>Photosystem II (PSII) uses the energy from red light to split water and reduce quinone, an energy-demanding process based on chlorophyll a (Chl-a) photochemistry. Two kinds of cyanobacterial PSII can use Chl-d and Chl-f to perform the same reactions using lower energy, far-red light. PSII from <jats:italic>Acaryochloris marina</jats:italic> has Chl-d replacing all but one of its 35 Chl-a, while PSII from <jats:italic>Chroococcidiopsis thermalis</jats:italic>, a facultative far-red species, has just 4 Chl-f and 1 Chl-d and 30 Chl-a. From bioenergetic considerations, the far-red PSII were predicted to lose photochemical efficiency and/or resilience to photodamage. Here, we compare enzyme turnover efficiency, forward electron transfer, back-reactions and photodamage in Chl-f-PSII, Chl-d-PSII and Chl-a-PSII. We show that: i) all types of PSII have a comparable efficiency in enzyme turnover; ii) the modified energy gaps on the acceptor side of Chl-d-PSII favor recombination via P<jats:sub>D1</jats:sub><jats:sup>+</jats:sup>Phe<jats:sup>-</jats:sup> repopulation, leading to increased singlet oxygen production and greater sensitivity to high-light damage compared to Chl-a-PSII and Chl-f-PSII; ii) the acceptor-side energy gaps in Chl-f-PSII are tuned to avoid harmful back reactions, favoring resilience to photodamage over efficiency of light usage. The results are explained by the differences in the redox tuning of the electron transfer cofactors Phe and Q<jats:sub>A</jats:sub> and in the number and layout of the chlorophylls that share the excitation energy with the primary electron donor. PSII has adapted to lower energy in two distinct ways, each appropriate for its specific environment but with different functional penalties.</jats:p>
Fantuzzi A, Allgower F, Baker H, et al., 2022, Bicarbonate-controlled reduction of oxygen by the QA semiquinone in Photosystem II in membranes, Proceedings of the National Academy of Sciences of USA, Vol: 119, ISSN: 0027-8424
Photosystem II (PSII), the water/plastoquinone photo-oxidoreductase, plays a key energy input role in the biosphere. Q∙−A, the reduced semiquinone form of the nonexchangeable quinone, is often considered capable of a side reaction with O2, forming superoxide, but this reaction has not yet been demonstrated experimentally. Here, using chlorophyll fluorescence in plant PSII membranes, we show that O2 does oxidize Q∙−A at physiological O2 concentrations with a t1/2 of 10 s. Superoxide is formed stoichiometrically, and the reaction kinetics are controlled by the accessibility of O2 to a binding site near Q∙−A, with an apparent dissociation constant of 70 ± 20 µM. Unexpectedly, Q∙−A could only reduce O2 when bicarbonate was absent from its binding site on the nonheme iron (Fe2+) and the addition of bicarbonate or formate blocked the O2-dependant decay of Q∙−A. These results, together with molecular dynamics simulations and hybrid quantum mechanics/molecular mechanics calculations, indicate that electron transfer from Q∙−A to O2 occurs when the O2 is bound to the empty bicarbonate site on Fe2+. A protective role for bicarbonate in PSII was recently reported, involving long-lived Q∙−A triggering bicarbonate dissociation from Fe2+ [Brinkert et al., Proc. Natl. Acad. Sci. U.S.A. 113, 12144–12149 (2016)]. The present findings extend this mechanism by showing that bicarbonate release allows O2 to bind to Fe2+ and to oxidize Q∙−A. This could be beneficial by oxidizing Q∙−A and by producing superoxide, a chemical signal for the overreduced state of the electron transfer chain.
Fantuzzi A, Haniewicz P, Farci D, et al., 2022, Bicarbonate Activation of Monomeric Photosystem II-PsbS/Psb27 Complex
<jats:title>Abstract</jats:title><jats:p>In thylakoid membranes, Photosystem II monomers from the stromal lamellae contain the subunits PsbS and Psb27 (PSIIm-S/27), while Photosystem II monomers from granal regions (PSIIm) lack these subunits. Here, we have isolated and characterised these two types of Photosystem II complexes. The PSIIm-S/27 showed enhanced fluorescence, the near-absence of oxygen evolution, as well as limited and slow electron transfer from Q<jats:sub>A</jats:sub> to Q<jats:sub>B</jats:sub> compared to the near-normal activities in the granal PSIIm. However, when bicarbonate was added to the PSIIm-S/27, water splitting and Q<jats:sub>A</jats:sub> to Q<jats:sub>B</jats:sub> electron transfer rates were comparable to those in granal PSIIm. The findings suggest that the binding of PsbS and/or Psb27 inhibits forward electron transfer and lowers the binding affinity for the bicarbonate. This can be rationalized in terms of the recently discovered photoprotection role played by bicarbonate binding via the redox tuning of the Q<jats:sub>A</jats:sub>/Q<jats:sub>A</jats:sub><jats:sup>•−</jats:sup> couple, which controls the charge recombination route, and this limits chlorophyll triplet mediated <jats:sup>1</jats:sup>O<jats:sub>2</jats:sub> formation (Brinkert K et al. (2016) Proc Natl Acad Sci U S A. 113(43):12144-12149). These findings suggest that PSIIm-S/27 is an intermediate in the assembly of PSII in which PsbS and/or Psb27 restrict PSII activity while in transit, by using a bicarbonate-mediated switch and protective mechanism.</jats:p><jats:sec><jats:title>One sentence summary</jats:title><jats:p>A photosystem II monomer with PsbS and Psb27 as additional subunits, is inactive as isolated but activated by bicarbonate, and is attributed to be a late-stage intermediate in photoassembly.&l
Varghese F, Kabasakal B, Cotton C, et al., 2021, A Low-Potential Terminal Oxidase Associated with the Iron-Only Nitrogenase from the Nitrogen-Fixing Bacterium Azotobacter vinelandii, Experimental Biology Meeting, Publisher: WILEY, ISSN: 0892-6638
Judd M, Morton J, Nurnberg D, et al., 2020, The primary donor of far-red photosystem II: Chl(D1) or P-D2?, BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, Vol: 1861, ISSN: 0005-2728
- Author Web Link
- Citations: 7
Babacan O, De Causmaecker S, Gambhir A, et al., 2020, Assessing the feasibility of carbon dioxide mitigation options in terms of energy usage, Nature Energy, Vol: 5, Pages: 720-728, ISSN: 2058-7546
Measures to mitigate the emissions of carbon dioxide (CO2) can vary substantially in terms of the energy required. Some proposed CO2 mitigation options involve energy-intensive processes that compromise their viability as routes to mitigation, especially if deployed at a global scale. Here we provide an assessment of different mitigation options in terms of their energy usage. We assess the relative effectiveness of several CO2 mitigation routes by calculating the energy cost of carbon abatement (kilowatt-hour spent per kilogram CO2-equivalent, or kWh kgCO2e–1) mitigated. We consider energy efficiency measures, decarbonizing electricity, heat, chemicals and fuels, and also capturing CO2 from air. Among the routes considered, switching to renewable energy technologies (0.05–0.53 kWh kgCO2e–1 mitigated) offer more energy-effective mitigation than carbon embedding or carbon removal approaches, which are more energy intensive (0.99–10.03 kWh kgCO2e–1 and 0.78–2.93 kWh kgCO2e–1 mitigated, respectively), whereas energy efficiency measures, such as improving building lighting, can offer the most energy-effective mitigation.
Zamzam N, Rakowski R, Kaucikas M, et al., 2020, Femtosecond visible transient absorption spectroscopy of chlorophyll f- containing Photosystem II, Proceedings of the National Academy of Sciences of USA, Vol: 117, Pages: 1-7, ISSN: 0027-8424
The recently discovered, chlorophyll-f-containing, far-red photosystem II (FR-PSII) supports far-red light photosynthesis. Participation and kinetics of spectrally shifted far-red pigments are directly observable and separated from that of bulk chlorophyll-a. We present an ultrafast transient absorption study of FR-PSII, investigating energy transfer and charge separation processes. Results show a rapid subpicosecond energy transfer from chlorophyll-a to the long-wavelength chlorophylls-f/d. The data demonstrate the decay of an ∼720-nm negative feature on the picosecond-to-nanosecond timescales, coinciding with charge separation, secondary electron transfer, and stimulated emission decay. An ∼675-nm bleach attributed to the loss of chl-a absorption due to the formation of a cation radical, PD1+•, is only fully developed in the nanosecond spectra, indicating an unusually delayed formation. A major spectral feature on the nanosecond timescale at 725 nm is attributed to an electrochromic blue shift of a FR-chlorophyll among the reaction center pigments. These time-resolved observations provide direct experimental support for the model of Nürnberg et al. [D. J. Nürnberg et al., Science 360, 1210–1213 (2018)], in which the primary electron donor is a FR-chlorophyll and the secondary donor is chlorophyll-a (PD1 of the central chlorophyll pair). Efficient charge separation also occurs using selective excitation of long-wavelength chlorophylls-f/d, and the localization of the excited state on P720* points to a smaller (entropic) energy loss compared to conventional PSII, where the excited state is shared over all of the chlorin pigments. This has important repercussions on understanding the overall energetics of excitation energy transfer and charge separation reactions in FR-PSII.
Shevela D, Do H-N, Fantuzzi A, et al., 2020, Bicarbonate-Mediated CO2 Formation on Both Sides of Photosystem II, BIOCHEMISTRY, Vol: 59, Pages: 2442-2449, ISSN: 0006-2960
- Author Web Link
- Citations: 12
De Causmaecker S, Douglass J, Fantuzzi A, et al., 2019, Energetics of the exchangeable quinone, QB, in Photosystem II, Proceedings of the National Academy of Sciences of USA, Vol: 116, Pages: 19458-19463, ISSN: 0027-8424
Photosystem II (PSII), the light-driven water/plastoquinone photo-oxidoreductase, is of central importance in the planetary energy cycle. The product of the reaction, plastohydroquinone (PQH2), is released into the membrane from the QB-site, where it is formed. A plastoquinone (PQ) from the membrane pool then binds into the QB-site. Despite their functional importance, the thermodynamic properties of the PQ in the QB-site, QB, in its different redox forms have received relatively little attention. Here we report the midpoint potentials (Em) of QB in PSII from Thermosynechococcus elongatus using EPR spectroscopy: Em QB/QB•−≈ 90 mV and Em QB•−/QBH2≈ 40 mV. These data allow the following conclusions: 1) the semiquinone, QB•−, is stabilized thermodynamically; 2) the resulting Em QB/QBH2 (~ 65 mV) is lower than the EmPQ/PQH2 (~117 mV), and the difference (ΔE ~50 meV) represents the driving force for QBH2 release into the pool; 3) PQ is ~ 50x more tightly bound than PQH2; 4) the difference between the Em QB/QB•− measured here and the Em QA/QA•− from the literature is ~234 meV, in principle corresponding to the driving force for electron transfer from QA•− to QB. The pH-dependence of the thermoluminescence associated with QB•− provided a functional estimate for this energy gap and gave a similar value (≥180 meV). These estimates are larger than the generally accepted value (~70 meV) and this is discussed. The energetics of QB in PSII are comparable to those in the homologous purple bacterial reaction center.
Varghese F, Kabasakal BV, Cotton CA, et al., 2019, A low-potential terminal oxidase associated with the iron-only nitrogenase from the nitrogen-fixing bacterium Azotobacter vinelandii, Journal of Biological Chemistry, Vol: 294, Pages: 9367-9376, ISSN: 0021-9258
The biological route for nitrogen gas entering the biosphere is reduction to ammonia by the nitrogenase enzyme, which is inactivated by oxygen. Three types of nitrogenase exist, the least studied of which is the iron-only nitrogenase. The Anf3 protein in the bacterium Rhodobacter capsulatus is essential for diazotrophic (i.e. nitrogen-fixing) growth with the iron-only nitrogenase, but its enzymatic activity and function are unknown. Here, we biochemically and structurally characterize Anf3 from the model diazotrophic bacterium Azotobacter vinelandii. Determining the Anf3 crystal structure to atomic resolution, we observed that it is a dimeric flavocytochrome with an unusually close interaction between the heme and the flavin adenine dinucleotide cofactors. Measuring the reduction potentials by spectroelectrochemical redox titration, we observed values of -420 ± 10 mV and -330 ± 10 mV for the two FAD potentials and -340 ± 1 mV for the heme. We further show that Anf3 accepts electrons from spinach ferredoxin and that Anf3 consumes oxygen without generating superoxide or hydrogen peroxide. We predict that Anf3 protects the iron-only nitrogenase from oxygen inactivation by functioning as an oxidase in respiratory protection, with flavodoxin or ferredoxin as the physiological electron donors.
Kornienko N, Zhang JZ, Sokol K, et al., 2018, Oxygenic photoreactivity in photosystem II studied by rotating ring disk electrochemistry, Journal of the American Chemical Society, Vol: 140, Pages: 17923-17931, ISSN: 1520-5126
Protein film photoelectrochemistry has previously been used to monitor the activity of Photosystem II, the water-plastoquinone photooxidoreductase, but the mechanistic information attainable from a three-electrode setup has remained limited. Here we introduce the four-electrode rotating ring disk electrode technique for quantifying light-driven reaction kinetics and mechanistic pathways in real time at the enzyme-electrode interface. This setup allows us to study photochemical H2O oxidation in Photosystem II and to gain in-depth understanding of pathways that generate reactive oxygen species. The results show that Photosystem II reacts with O2 through two main pathways that both involve a superoxide intermediate to produce H2O2. The first pathway involves the established chlorophyll triplet-mediated formation of singlet oxygen, which is followed by its reduction to superoxide at the electrode surface. The second pathway is specific for the enzyme/electrode interface: an exposed antenna chlorophyll is sufficiently close to the electrode for rapid injection of an electron to form a highly reducing chlorophyll anion, which reacts with O2 in solution to produce O2•-. Incomplete H2O oxidation does not significantly contribute to reactive oxygen formation in our conditions. The rotating ring disk electrode technique allows the chemical reactivity of Photosystem II to be studied electrochemically and opens several avenues for future investigation.
Sawa M, Fantuzzi A, Nixon P, et al., 2018, Development of printed solar biobattery for use in bioelectronics, Arm Summit 2018, Publisher: Arm
There is an urgent need to develop a sustainable battery technology that is cheap, environmentally friendly, easy to fabricate and to dispose of, especially to tackle the world-wide increase in illegally dumped electronic wastes. Microbial biophotovoltaic (BPV) technology is a renewable bioenergy system currently being developed at the laboratory scale. It generates electricity from the photosynthetic metabolism of cyanobacteria and microalgae and exploits their ability to convert light energy into electrical current using water as the source of electrons. Innovative approaches are needed to solve scale-up issues such as cost, ease of fabrication (particularly the fabrication of the inorganic and biological (microbes) parts).In this talk, I will report the feasibility of using a simple commercial thermal-inkjet printer to fabricate a thin-film paper-based BPV cell consisting of a layer of cyanobacterial cells on top of a carbon nanotube conducting surface on plain copy paper. The digitally printed thin-film BPV system produced electricity both in the light and dark, with a maximum electrical power output of 0.38 mW m-2 in one system and the sustained electrical current production over 100 hours in another more fully printed system. I will address limitations and challenges as well possible applications in the area of printed bioelectronics.
Messant M, Timm S, Fantuzzi A, et al., 2018, Glycolate Induces Redox Tuning Of Photosystem II in Vivo: Study of a Photorespiration Mutant, PLANT PHYSIOLOGY, Vol: 177, Pages: 1277-1285, ISSN: 0032-0889
- Author Web Link
- Citations: 17
Nuernberg DJ, Morton J, Santabarbara S, et al., 2018, Photochemistry beyond the red limit in chlorophyll f-containing photosystems, Science, Vol: 360, Pages: 1210-1213, ISSN: 0036-8075
Photosystems I and II convert solar energy into the chemical energy that powers life. Chlorophyll a photochemistry, using red light (680 to 700 nm), is near universal and is considered to define the energy “red limit” of oxygenic photosynthesis. We present biophysical studies on the photosystems from a cyanobacterium grown in far-red light (750 nm). The few long-wavelength chlorophylls present are well resolved from each other and from the majority pigment, chlorophyll a. Charge separation in photosystem I and II uses chlorophyll f at 745 nm and chlorophyll f (or d) at 727 nm, respectively. Each photosystem has a few even longer-wavelength chlorophylls f that collect light and pass excitation energy uphill to the photochemically active pigments. These photosystems function beyond the red limit using far-red pigments in only a few key positions.
Zhang JZ, Bombelli P, Sokol KP, et al., 2018, Photoelectrochemistry of Photosystem II &ITin Vitro&IT vs&IT in Vivo&IT, Journal of the American Chemical Society, Vol: 140, Pages: 6-9, ISSN: 1520-5126
Factors governing the photoelectrochemical output of photosynthetic microorganisms are poorly understood, and energy loss may occur due to inefficient electron transfer (ET) processes. Here, we systematically compare the photoelectrochemistry of photosystem II (PSII) protein-films to cyanobacteria biofilms to derive: (i) the losses in light-to-charge conversion efficiencies, (ii) gains in photocatalytic longevity, and (iii) insights into the ET mechanism at the biofilm interface. This study was enabled by the use of hierarchically structured electrodes, which could be tailored for high/stable loadings of PSII core complexes and Synechocystis sp. PCC 6803 cells. The mediated photocurrent densities generated by the biofilm were 2 orders of magnitude lower than those of the protein-film. This was partly attributed to a lower photocatalyst loading as the rate of mediated electron extraction from PSII in vitro is only double that of PSII in vivo. On the other hand, the biofilm exhibited much greater longevity (>5 days) than the protein-film (<6 h), with turnover numbers surpassing those of the protein-film after 2 days. The mechanism of biofilm electrogenesis is suggested to involve an intracellular redox mediator, which is released during light irradiation.
Sawa M, Fantuzzi A, Bombelli P, et al., 2017, Electricity generation from digitally printed cyanobacteria, Nature Communications, Vol: 8, Pages: 1-10, ISSN: 2041-1723
Microbial biophotovoltaic cells exploit the ability of cyanobacteria and microalgae to convert light energy into electrical current using water as the source of electrons. Such bioelectrochemical systems have a clear advantage over more conventional microbial fuel cells which require the input of organic carbon for microbial growth. However, innovative approaches are needed to address scale-up issues associated with the fabrication of the inorganic (electrodes) and biological (microbe) parts of the biophotovoltaic device. Here we demonstrate the feasibility of using a simple commercial inkjet printer to fabricate a thin-film paper-based biophotovoltaic cell consisting of a layer of cyanobacterial cells on top of a carbon nanotube conducting surface. We show that these printed cyanobacteria are capable of generating a sustained electrical current both in the dark (as a ‘solar bio-battery’) and in response to light (as a ‘bio-solar-panel’) with potential applications in low-power devices.
Rutherford AW, Fantuzzi A, Brinkert K, et al., 2016, Bicarbonate-induced redox tuning in Photosystem II for regulation and protection, Proceedings of the National Academy of Sciences of the United States of America, Vol: 113, Pages: 12144-12149, ISSN: 1091-6490
The midpoint potential (Em) of QA/Q−∙AQA/QA−•, the one-electron acceptor quinone of Photosystem II (PSII), provides the thermodynamic reference for calibrating PSII bioenergetics. Uncertainty exists in the literature, with two values differing by ∼80 mV. Here, we have resolved this discrepancy by using spectroelectrochemistry on plant PSII-enriched membranes. Removal of bicarbonate (HCO3−) shifts the Em from ∼−145 mV to −70 mV. The higher values reported earlier are attributed to the loss of HCO3− during the titrations (pH 6.5, stirred under argon gassing). These findings mean that HCO3− binds less strongly when QA−• is present. Light-induced QA−• formation triggered HCO3− loss as manifest by the slowed electron transfer and the upshift in the Em of QA. HCO3−-depleted PSII also showed diminished light-induced 1O2 formation. This finding is consistent with a model in which the increase in the Em of QA/Q−∙AQA/QA−• promotes safe, direct P+∙Q−∙AP+•QA−• charge recombination at the expense of the damaging back-reaction route that involves chlorophyll triplet-mediated 1O2 formation [Johnson GN, et al. (1995) Biochim Biophys Acta 1229:202–207]. These findings provide a redox tuning mechanism, in which the interdependence of the redox state of QA and the binding by HCO3− regulates and protects PSII. The potential for a sink (CO2) to source (PSII) feedback mechanism is discussed.
Brinkert K, Le formal F, Li X, et al., 2016, Photocurrents from photosystem II in a metal oxide hybrid system: electron transfer pathways, Biochimica et Biophysica Acta-Bioenergetics, Vol: 1857, Pages: 1497-1505, ISSN: 0005-2728
We have investigated the nature of the photocurrent generated by Photosystem II (PSII), the water oxidising enzyme, isolated from Thermosynechococcus elongatus, when immobilized on nanostructured titanium dioxide on an indium tin oxide electrode (TiO2/ITO). We investigated the properties of the photocurrent from PSII when immobilized as a monolayer versus multilayers, in the presence and absence of an inhibitor that binds to the site of the exchangeable quinone (QB) and in the presence and absence exogenous mobile electron carriers (mediators). The findings indicate that electron transfer occurs from the first quinone (QA) directly to the electrode surface but that the electron transfer through the nanostructured metal oxide is the rate-limiting step. Redox mediators enhance the photocurrent by taking electrons from the nanostructured semiconductor surface to the ITO electrode surface not from PSII. This is demonstrated by photocurrent enhancement using a mediator incapable of accepting electrons from PSII. This model for electron transfer also explains anomalies reported in the literature using similar and related systems. The slow rate of the electron transfer step in the TiO2 is due to the energy level of electron injection into the semiconducting material being below the conduction band. This limits the usefulness of the present hybrid electrode. Strategies to overcome this kinetic limitation are discussed.
Cotton CA, Douglass JS, De Causmaecker S, et al., 2015, Photosynthetic constraints on fuel from microbes., Frontiers in Bioengineering and Biotechnology, Vol: 3, ISSN: 2296-4185
Valetti F, Fantuzzi A, Sadeghi SJ, et al., 2012, Iron-based redox centres of reductase and oxygenase components of phenol hydroxylase from A. radioresistens: a redox chain working at highly positive redox potentials, METALLOMICS, Vol: 4, Pages: 72-77, ISSN: 1756-5901
- Author Web Link
- Citations: 2
Fantuzzi A, Mak LH, Capria E, et al., 2011, A New Standardized Electrochemical Array for Drug Metabolic Profiling with Human Cytochromes P450, Analytical Chemistry, Vol: 83, Pages: 3831-3839, ISSN: 0003-2700
Panicco P, Dodhia VR, Fantuzzi A, et al., 2011, Enzyme-Based Amperometric Platform to Determine the Polymorphic Response in Drug Metabolism by Cytochromes P450, ANALYTICAL CHEMISTRY, Vol: 83, Pages: 2179-2186, ISSN: 0003-2700
- Author Web Link
- Citations: 40
Sadeghi SJ, Fantuzzi A, Gilardi G, 2011, Breakthrough in P450 bioelectrochemistry and future perspectives, BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS, Vol: 1814, Pages: 237-248, ISSN: 1570-9639
- Author Web Link
- Citations: 97
Fantuzzi A, Capria E, Mak LH, et al., 2010, An Electrochemical Microfluidic Platform for Human P450 Drug Metabolism Profiling, Analytical Chemistry, Vol: 82, Pages: 10222-10227, ISSN: 0003-2700
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